This invention relates to a braking or retarding device for slowing down and controlling the speed of moving objects such as cartons, pallets and the like travelling on a roller conveyor system. More particularly, the invention relates to a simplified braking or retarding device for conveyors which obviates the need for complex mechanical or electro-mechanical mechanisms commonly known in the prior art.
The use of inclined conveyors using feely rotatable wheels or rollers for the travel of pallets and the like objects thereon by the use of gravity is well known. A gradient such as 1.5.degree. has been found satisfactory to overcome friction and to permit the free flow of pallets on conveyors, but such a slope can result in continued acceleration of the pallets along the conveyors and, if the travel of the pallets is not retarded and controlled, the forward velocity of the pallets can unduly increase resulting in collisions and damage both to pallets and their contents with possible danger to workmen and other personnel.
A number of speed retarders for gravity conveyors have been designed in an effort to overcome the problems inherent in this type of flow conveyor. For example, U.S. Pat. No. 3,321,057 discloses a retarder for gravity conveyors comprising inter alia a retarder roller adapted to engage a brake pad which is disposed in a positive braking position by a solenoid-actuated latch in electrical communication with a timer. Upon depression of the retarder roller, the timer is actuated releasing the roller brake upon expiration of a timed interval; thus sequentially controlling a plurality of articles travelling on the gravity conveyor. This apparatus requires the use of an electrically operated timing device and does not permit actuation and release of the retarder roller upon removal of a particular article from the gravity conveyor.
U.S. Pat. No. 1,425,599 teaches a gravity conveyor having retarding means for maintaining an interval of space between articles passing over the said conveyor to prevent collision of articles transported. The structure comprises a retarding device actuated by an article passing thereover whereby a plurality of brake shoes engages a corresponding number of retarding rollers upon actuation of a hinged conveyor section. However, the structure is complex in design and expensive to manufacture.